1. Field of the Invention
This invention relates to a real image mode finder optical system used in a camera for halide films, a digital camera, or a video camera.
2. Description of Related Art
A real image mode finder optical system has been used to make sure of a visual field for photography. In order to prevent flare produced by this real image mode finder optical system, various proposals have been made. For example, Japanese Patent Preliminary Publication No. Hei 9-211547 discloses a light-blocking means for preventing flare caused by a strong refracting power on the periphery of a lens in a finder when a pupil position is shifted from the optical axis. On the other hand, Japanese Patent Preliminary Publication No. Hei 6-95215 discusses a light-blocking means for eliminating stray light due to a light beam which is not reflected in an image erecting optical system.
However, no account is taken of light reflected by the end face of the periphery of a lens in any of technical prior art articles including the above publications, and thus flare or ghost is produced by reflected light. Alternatively, in order to prevent such flare, it is necessary to increase the diameter of a lens itself in the finder. This causes oversizing of the finder.
It is, therefore, a primary object of the present invention to provide a real image mode finder optical system which suppresses the production of ghost or flare, without enlarging a lens itself, and has a good view.
It is another object of the present invention to provide a real image mode finder optical system which has a configuration suitable for a reduction in the overall length.
It is still another object of the present invention to provide a real image mode finder optical system or lens which has a good view even when a lens with a gate produced in injection molding thereof is used.
In order to achieve the above objects, according to one aspect of the present invention, the real image mode finder optical system includes an objective optical system with a positive refracting power, an image erecting optical system having a plurality of reflecting sections for erecting an image formed by the objective optical system, and an ocular optical system for introducing an erected image into an observer""s eye. In this case, at least one lens of the objective optical system or the ocular optical system is configured to be rotational asymmetrical with respect to the optical axis, and a light-blocking means for blocking reflected light at the end face of the lens is provided adjacent to the lens or spaced away therefrom through air.
According to another aspect of the present invention, the real image mode finder optical system includes an objective optical system with a positive refracting power, an image erecting optical system having a plurality of reflecting sections for erecting an image formed by the objective optical system, and an ocular optical system for introducing an image erected by the image erecting optical system into an observer""s eye. In this case, an angle at which the optical axis is bent by the most object-side reflecting section of the image erecting optical system is acute, and the most image-side lens of the objective optical system is configured so that its end directed toward the optical axis bent by the most object-side reflecting section is cut out.
According to still another aspect of the present invention, the real image mode finder optical system is constructed so that an angle at which the optical axis is bent by the most object-side reflecting section of the image erecting optical system is acute, and at least one lens of the objective optical system is one of lenses constituting the objective optical system and has a shape that its end directed toward the optical axis bent by the most object-side reflecting section is cut out.
These and other objects as well as the features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.